Ink jet printing process

ABSTRACT

An ink jet printing process for improving the ozone stability an ink jet image comprising: 
     a) providing an ink jet recording element comprising a support having thereon a porous image-receiving layer having interconnecting voids; and 
     b) applying droplets of a liquid ink on the image-receiving layer in an image-wise manner, the ink comprising water, humectant and a metallized, phthalocyanine dye, the metallized, phthalocyanine dye comprising the formula: 
     
       
         MPc(SO 3 X) a (SO 2 NRR′) b .

CROSS REFERENCE TO RELATED APPLICATION

Reference is made to commonly assigned, co-pending U.S. patentapplication Ser. No. 09/813,760 by Andrievsky et al., filed concurrentlyherewith entitled “Ink Jet Printing Process”.

FIELD OF THE INVENTION

This invention relates to an ink jet printing process for improving theozone stability of an ink jet image.

BACKGROUND OF THE INVENTION

Ink jet printing is a non-impact method for producing images by thedeposition of ink droplets in a pixel-by-pixel manner to animage-recording element in response to digital signals. There arevarious methods which may be utilized to control the deposition of inkdroplets on the image-recording element to yield the desired image. Inone process, known as continuous ink jet, a continuous stream ofdroplets is charged and deflected in an imagewise manner onto thesurface of the image-recording element, while unimaged droplets arecaught and returned to an ink sump. In another process, known asdrop-on-demand ink jet, individual ink droplets are projected as neededonto the image-recording element to form the desired image. Commonmethods of controlling the projection of ink droplets in drop-on-demandprinting include piezoelectric transducers and thermal bubble formation.Ink jet printers have found broad applications across markets rangingfrom industrial labeling to short run printing to desktop document andpictorial imaging.

The inks used in the various ink jet printers can be classified aseither dye-based or pigment-based. A dye is a colorant which ismolecularly dispersed or solvated by a carrier medium. The carriermedium can be a liquid or a solid at room temperature. A commonly usedcarrier medium is water or a mixture of water and organic co-solvents.Each individual dye molecule is surrounded by molecules of the carriermedium. In dye-based inks, no particles are observable under themicroscope. Although there have been many recent advances in the art ofdye-based ink jet inks, such inks still suffer from deficiencies such aslow optical densities on plain paper and poor light-fastness. When wateris used as the carrier medium, such inks also generally suffer from poorwater-fastness.

The ink jet receiving elements that can be used with the above mentionedinks must meet several requirements including producing high densityimages that will not smear, bleed or wander when exposed to water forshort periods of time.

U.S. Pat. Nos. 6,149,722 and 6,015,896, WO 00/08103 and WO 98/49239relate to inks containing phthalocyanine dyes used in ink jet printing.However, there is no disclosure in these references that these inkswould be useful with a recording element containing a porousimage-receiving layer.

It is an object of this invention to provide an ink jet printing processfor improving the ozone stability of an ink jet image.

SUMMARY OF THE INVENTION

These and other objects are achieved in accordance with the presentinvention which comprises an ink jet printing process for improving theozone stability of an ink jet image comprising:

a) providing an ink jet recording element comprising a support havingthereon a porous image-receiving layer having interconnecting voids; and

b) applying droplets of a liquid ink on the image-receiving layer in animage-wise manner, the ink comprising water, humectant and a metallized,phthalocyanine dye, the metallized, phthalocyanine dye comprising theformula:

MPc(SO₃X)_(a)(SO₂NRR′)_(b)

wherein:

M represents a metal; such as copper, nickel, aluminum, zinc, iron orcobalt.

Pc represents a phthalocyanine nucleus;

X represents hydrogen, alkali metal or an organic cation;

a is from 0 to 2;

R represents hydrogen; a substituted or unsubstituted alkyl group havingfrom about 1 to about 15 carbon atoms, a substituted or unsubstitutedaryl group, or a substituted or unsubstituted heterocyclic group;

R′ represents an amino acid radical or at least one substituted orunsubstituted alkyl, aryl or heterocyclic substituent containing aprimary, secondary, tertiary or quaternary amino group which may be partof a cyclic ring; and

b is from 1 to 4, with the proviso that a+b is an average of from 3 to4.

It was found that the ozone stability of an ink jet image was improvedusing the compounds described herein.

DETAILED DESCRIPTION OF THE INVENTION

In a preferred embodiment of the invention, the metallized,phthalocyanine dyes which may be used include the following:

 MPc(SO₃X)_(a)(SO₂NHR′)_(b)

(M is Cu, and X, Pc, a and b being defined as above)

TABLE 1 Dye R′ 1

2

3

4

5

6

7

8

9

10

 MPc(SO₃X)_(a)(SO₂NHR′)_(b)

(M is Ni, and X, Pc, a and b being defined as above)

TABLE 2 Dye R′ 11

12

The dyes described above may be employed in any amount effective for theintended purpose. In general, good results have been obtained when thedye is present in an amount of from about 0.2 to about 5% by weight ofthe ink jet ink composition, preferably from about 0.3 to about 3% byweight. Dye mixtures may also be used.

The support for the ink jet recording element used in the invention canbe any of those usually used for ink jet receivers, such as paper,resin-coated paper, plastics such as a polyester-type resin such aspoly(ethylene terephthalate), polycarbonate resins, polysulfone resins,methacrylic resins, cellophane, acetate plastics, cellulose diacetate,cellulose triacetate, vinyl chloride resins, poly(ethylene naphthalate),polyester diacetate, various glass materials, and microporous materialssuch as microvoided polyester described in copending U.S. Ser. No.09/650,129, filed Aug. 29, 2000, polyethylene polymer-containingmaterial sold by PPG Industries, Inc., Pittsburgh, Pennsylvania underthe trade name of Teslin® Tyvek® synthetic paper (DuPont Corp.), andOPPalyte® films (Mobil Chemical Co.) and other composite films listed inU.S. Pat. No. 5,244,861. The thickness of the support employed in theinvention can be, for example, from about 12 to about 500 μm, preferablyfrom about 75 to about 300 μm.

Antioxidants, antistatic agents, plasticizers and other known additivesmay be incorporated into the support, if desired. In a preferredembodiment, paper is employed.

In a preferred embodiment of the invention the porous ink-receptivelayer contains inorganic particles such as silica, alumina, titaniumdioxide, clay, calcium carbonate, barium sulfate, or zinc oxide. Inanother preferred embodiment, the porous ink-receptive layer comprisesfrom about 30% to about 95% inorganic particles and from about 5% toabout 70% polymeric binder, such as gelatin, poly(vinyl alcohol),poly(vinyl pyrrolidinone) or poly(vinyl acetate). The porousink-receptive layer can also contain organic beads or polymericmicro-porous structures without inorganic filler particles as shown inU.S. Pat. Nos. 5,374,475 and 4,954,395, the disclosures of which arehereby incorporated by reference. The porous image-receiving layercomprises from about 10% to about 95% inorganic particles and from about5% to about 90% of a polymeric binder.

Examples of binders which may be used in the image-receiving layerinclude polyvinyl alcohol, polyvinyl pyrrolidone, poly(ethyl oxazoline),non-deionized or deionized Type IV bone gelatin, acid processed osseingelatin or pig skin gelatin. The hydrophilic polymer may be present inan amount of from about 0.4 to about 30 g/m², preferably from about 1 toabout 16 g/m².

The pH of the aqueous ink compositions of the invention may be adjustedby the addition of organic or inorganic acids or bases. Useful inks mayhave a preferred pH of from about 2 to 7, depending upon the type of dyebeing used. Typical inorganic acids include hydrochloric, phosphoric andsulfuric acids. Typical organic acids include methanesulfonic, aceticand lactic acids. Typical inorganic bases include alkali metalhydroxides and carbonates. Typical organic bases include ammonia,triethanolamine and tetramethylethylenediamine.

A humectant is employed in the ink jet composition of the invention tohelp prevent the ink from drying out or crusting in the orifices of theprinthead. Examples of humectants which can be used include polyhydricalcohols, such as ethylene glycol, diethylene glycol, triethyleneglycol, propylene glycol, tetraethylene glycol, polyethylene glycol,glycerol, 2-methyl-2,4-pentanediol 1,2,6-hexanetriol and thioglycol;lower alkyl mono- or di-ethers derived from alkylene glycols, such asethylene glycol mono-methyl or mono-ethyl ether, diethylene glycolmono-methyl or mono-ethyl ether, propylene glycol mono-methyl ormono-ethyl ether, triethylene glycol mono-methyl or mono-ethyl ether,diethylene glycol di-methyl or di-ethyl ether, and diethylene glycolmonobutylether; nitrogen-containing cyclic compounds, such aspyrrolidone, N-methyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone;and sulfur-containing compounds such as dimethyl sulfoxide andtetramethylene sulfone. A preferred humectant for the composition of theinvention is diethylene glycol, glycerol, or diethylene glycolmonobutylether.

Water-miscible organic solvents may also be added to the aqueous ink ofthe invention to help the ink penetrate the receiving substrate,especially when the substrate is a highly sized paper. Examples of suchsolvents include alcohols, such as methyl alcohol, ethyl alcohol,n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol,t-butyl alcohol, iso-butyl alcohol, furfuryl alcohol, andtetrahydrofurfuryl alcohol; ketones or ketoalcohols such as acetone,methyl ethyl ketone and diacetone alcohol; ethers, such astetrahydrofuran and dioxane; and esters, such as, ethyl lactate,ethylene carbonate and propylene carbonate.

Surfactants may be added to adjust the surface tension of the ink to anappropriate level. The surfactants may be anionic, cationic, amphotericor nonionic. A preferred surfactant for the ink composition of thepresent invention is Surfynol® 465 (Air Products) at a finalconcentration of 0.1% to 1.0%.

A biocide may be added to the composition of the invention to suppressthe growth of micro-organisms such as molds, fungi, etc. in aqueousinks. A preferred biocide for the ink composition of the presentinvention is Proxel® GXL (Zeneca Specialties Co.) at a finalconcentration of 0.05-0.5 wt. %.

A typical ink composition of the invention may comprise, for example,the following substituents by weight: colorant (0.2-5%), water (20-95%),humectant (5-70%), water miscible co-solvents (2-20%), surfactant(0.1-10%), biocide (0.05-5%) and pH control agents (0.1-10%).

Additional additives which may optionally be present in the ink jet inkcomposition of the invention include thickeners, conductivity enhancingagents, anti-kogation agents, drying agents, and defoamers.

The image-recording layer used in the process of the present inventioncan also contain various known additives, including matting agents suchas titanium dioxide, zinc oxide, silica and polymeric beads such ascrosslinked poly(methyl methacrylate) or polystyrene beads for thepurposes of contributing to the non-blocking characteristics and tocontrol the smudge resistance thereof; surfactants such as non-ionic,hydrocarbon or fluorocarbon surfactants or cationic surfactants, such asquaternary ammonium salts; fluorescent dyes; pH controllers;anti-foaming agents; lubricants; preservatives; viscosity modifiers;dye-fixing agents; waterproofing agents; dispersing agents; UV-absorbingagents; mildew-proofing agents; mordants; antistatic agents,anti-oxidants, optical brighteners, and the like. A hardener may also beadded to the ink-receiving layer if desired.

In order to improve the adhesion of the image-recording layer to thesupport, the surface of the support may be subjected to a treatment suchas a corona-discharge-treatment prior to applying the image-recordinglayer.

In addition, a subbing layer, such as a layer formed from a halogenatedphenol or a partially hydrolyzed vinyl chloride-vinyl acetate copolymercan be applied to the surface of the support to increase adhesion of theimage recording layer. If a subbing layer is used, it should have athickness (i.e., a dry coat thickness) of less than about 2 μm.

The image-recording layer may be present in any amount which iseffective for the intended purpose. In general, good results areobtained when it is present in an amount of from about 2 to about 46g/m², preferably from about 6 to about 16 g/m², which corresponds to adry thickness of about 2 to about 42 μm, preferably about 6 to about 15μm.

The following examples are provided to illustrate the invention.

EXAMPLES

Synthesis of Compound 1

Compound 1 as illustrated above was prepared as follows: Copperphthalocyanine (14 g) was added to chlorosulfonic acid (125 g) over 45minutes, while keeping the temperature below 40° C. The mixture was thenheated to 140-150° C. and stirred for 5 hours. After cooling to roomtemperature, thionyl chloride (49 g) was added dropwise over 30 minutes,and the mixture kept at 80° C. for 3 hrs. After cooling to roomtemperature, the mixture was poured on ice and stirred vigorously, whilekeeping the temperature below 5° C. The precipitate was filtered off,washed extensively with water at 5° C., and dried.1-(3-Aminopropyl)-imidazole (24 g) and pyridine (90 g) were dissolved in1-methyl-2-pyrrolidinone (70 mL). Phthalocyanine filter cake wasdissolved in 1-methyl-2-pyrrolidinone (150 mL) and added all at once tothe 1-(3-aminopropyl)-imidazole solution, and the reaction mixturestirred at room temperature for 3 hours, and then heated at 60° C. for 2hours. Ether (1 L) was added, and the mixture stirred for 1 hour.Liqueurs were decanted, and the residue suspended in boiling isopropylalcohol (500 mL), filtered, washed with isopropyl alcohol (100 mL), anddried to yield compound 1. The other compounds in Table 1 and nickelanalogs were prepared in a similar manner.

Example 1 Cu Phthalocyanine Dye

Recording Element 1

A coating solution for a base layer was prepared by combining fumedalumina (Cab-O-Sperse® PG003, Cabot Corp.), poly(vinyl alcohol)(Gohsenol® GH-23A, Nippon Gohsei Co., Ltd.) and2,3-dihydroxy-1,4-dioxane (Clariant Corp.) in a ratio of 88:10:2 to givean aqueous coating formulation of 30% solids by weight.

A coating solution for an image-receiving layer was prepared bycombining fumed alumina (Cab-O-Sperse® PG003, Cabot Corp.), poly(vinylalcohol) (Gohsenol® GH-23A, Nippon Gohsei Co.) and Polymer A in a ratioof 85:3:12 to give an aqueous coating formulation of 10% solids byweight. The fumed alumina particles have a primary particle size of fromabout 7 to about 40 nm in diameter and are aggregated up to about 150nm. Surfactants Zonyl® FSN (E. I. du Pont de Nemours and Co.) and Olin®10G (Dixie Chemical Co.) were added in small amounts as coating aids.

The above coating solutions were simultaneously bead-coated at 40° C. onpolyethylene-coated paper base which had been previously subjected tocorona discharge treatment. The image-receiving layer was coated on topof the base layer. The coating was then dried at 60° C. by forced air toyield a two-layer recording element in which the thicknesses of thebottom and topmost layers were 40 μm (43 g/m²) and 2 μm (2.2 g/m²),respectively.

Recording Element 2

The following commercially-available receiving element with a porousimage-receiving layer was used: Konica Photo Quality Ink Jet Paper QP,No: KJP-LT-GH-15-QP PI.

Preparation of Invention Inks

Inks containing the dyes employed in the invention as illustrated aboveand identified in Table 3 were prepared with de-ionized water containinghumectants of diethylene glycol and glycerol, each at 6%, a biocide,Proxel® GXL at 0.003 wt % and a surfactant, Surfynol® 465 (Air ProductsCo.) at 0.5 wt. %. In addition, for inks containing dyes 1, 8 and 10,lactic acid 1.0 wt. % was added. The dye concentrations were based onsolution absorption spectra and chosen such that the final ink whendiluted 1:1000, would yield a transmission optical density ofapproximately 1.0.

Preparation of Control Inks

These inks were prepared the same as the Invention Inks except that thefollowing control dyes were used which are metallized phthalocyaninedyes but which have different substituents than those set forth in theinvention:

C-1 Direct blue 199

C-2 CuPc(SO₃Na)_(a)(SO₂NH(CH₂)₃SO₃Na)_(b)

C-3 CuPc(SO₃Na)_(c); c is from 2 to 4.

(Pc and a are defined as above in the formula)

Printing of Test Images

The above prepared inks were filtered through a 0.45 μmpolytetrafluoroethylene filter and placed into an empty Lexmark inkcartridge, No: Lexmak 15MO120, and fitted into the ink station of aLexmark Z-51 printer. A test image consisting of 4 variable densitypatches approximately 10 by 10 mm in size, and ranging from 25% dotcoverage to 100% dot coverage was printed on to the following receivingelements: Element 1 above and Konica Photo Quality Ink Jet Paper QP, No:KJP-LT-GH-15-QP PI.

Evaluation of Test Images

For each ink, the Status A red reflection densities of the abovedescribed patches corresponding to 75% and 100% dot coverage weremeasured using an X-Rite 820 densitometer. The red density at 100% dotcoverage (d-max) is listed in the Table 2 below. The stepped images werethen placed in a dark chamber containing air and ozone gas at 5 ppm at50% RH for 3 days. The Status A densities of the stepped images werere-measured and the retained dye % in Status A red density for the 75%dot coverage patches were calculated for each ink and are also listed inthe following Table 2. A % retained value of greater than about 45% isconsidered to be acceptable.

TABLE 3 Ozone Fade % Retained Ink Containing Dye Recording Element 1Recording Element 2  1 63 71  2 59 62  3 49 61  4 69 70  5 92 93  6 7984  7 60 77  8 52 16  9 87 60 10 66 69 C-1 24 23 C-2 20 18 C-3 20 19

The above results show that the combination of the metallizedphthalocyanine dyes as described in the invention with a porousimage-receiving layer produced less fade than the control dyes in theozone test.

Example 2 Ni Phthalocyanine Dye

Preparation of Invention Inks

Inks were prepared similar to the invention inks in Example 1 above,except that they contained dyes 11 and 12.

Preparation of Control Ink

This ink was prepared the same as the above Invention Inks except thatthe following control dye was used which has different substituents thanthose set forth in the invention:

C-4 Nickel (II) phthalocyaninetetrasulfonic acid, tetrasodium salt(Aldrich Chemical Co.)

Printing of Test Images and Evaluation

The above prepared inks were printed and evaluated as in Example 1. Thefollowing results were obtained:

TABLE 4 Ozone Fade % Retained Ink Containing Dye Recording Element 1Recording Element 2 11 92 100 12 100 90 C-4 44 31

The above results show that the combination of the metallizedphthalocyanine dyes as described in the invention with a porousimage-receiving layer produced less fade than the control dyes in theozone test.

Although the invention has been described in detail with reference tocertain preferred embodiments for the purpose of illustration, it is tobe understood that variations and modifications can be made by thoseskilled in the art without departing from the spirit and scope of theinvention.

What is claimed is:
 1. An ink jet printing process for improving theozone stability of an ink jet image comprising: a) providing an ink jetrecording element comprising a support having thereon a porousimage-receiving layer having interconnecting voids; and b) applyingdroplets of a liquid ink on said image-receiving layer in an image-wisemanner, said ink comprising water, humectant and a metallized,phthalocyanine dye, said metallized, phthalocyanine dye comprising theformula: MPc(SO₃X)_(a)(SO₂NRR′)_(b) wherein: M represents a metal; Pcrepresents a phthalocyanine nucleus; X represents hydrogen, alkali metalor an organic cation; a is from 0 to2; R represents hydrogen; asubstituted or unsubstituted alkyl group having from about 1 to about 15carbon atoms, a substituted or unsubstituted aryl group, or asubstituted or unsubstituted heterocyclic group; R′ represents an aminoacid radical or at least one substituted or unsubstituted alkyl, aryl orheterocyclic substituent containing a primary, secondary, tertiary orquaternary amino group which may be part of a cyclic ring; and b is from1 to 4, with the proviso that a+b is an average of from 3 to
 4. 2. Theprocess of claim 1 wherein said porous image-receiving layer havinginterconnecting voids comprises organic or inorganic particulatematerials in a polymeric binder.
 3. The process of claim 2 wherein saidinorganic particles comprise silica, alumina, titanium dioxide, clay,calcium carbonate, barium sulfate, or zinc oxide.
 4. The process ofclaim 1 wherein said porous image-receiving layer comprises from about10% to about 95% inorganic particles and from about 5% to about 90% of apolymeric binder.
 5. The process of claim 4 wherein said polymericbinder is gelatin, poly(vinyl alcohol), poly(vinyl pyrrolidinone) orpoly(vinyl acetate).
 6. The process of claim 1 wherein said R representshydrogen.
 7. The process of claim 1 wherein said R′ represents


8. The process of claim 1 wherein M represents copper, nickel, aluminum,zinc, iron, or cobalt.
 9. The process of claim 7 wherein M represent Cuand R is H.
 10. The process of claim 1 wherein M represent Ni, R is H,and R′ is